Interlocking systems are used for ensuring the safety of trains. This master thesis is made in cooperation with Banedanmark and deals with relay-based interlocking systems for railway stations. The goal of this project is to develop a formal method for verifying that such systems guarantee the safety of trains. By using RSL models of interlocking systems, this thesis deduces an automated procedure for making an RSL-SAL transition system that denes the dynamic behaviour of an interlocking system. Also, the procedure specifies how to auto-generate confidence conditions for the generated transition system, formulated using Linear Temporal Logic (LTL). Finally, a tool for computing such a transition system and its associated confidence conditions is implemented using Java. Furthermore, this thesis develops patterns for specifying the behaviour of external inputs to an interlocking system (e.g. a rule can dene when a train can enter a station), formulated using RSL-SAL. Also, patterns for specifying safety properties are developed using LTL. Altogether, the tool and patterns define a method that uses the state-space based model checker SAL for verifying that interlocking systems guarantee the safety of trains. The method has successfully been applied to a Danish railway station.